Valveless combustion apparatus

ABSTRACT

Valveless combustion apparatus are disclosed in which a flame front from gas ignited in one part of the apparatus is utilized to ignite a charge of gas in another part of the apparatus that is open to atmosphere or other relatively low pressure. The ignition occurs before the charge of gas is dissipated from the part of the apparatus open to the lower pressure so that a high energy blast of gas can be directed from the apparatus to perform work. In one form of the combustion apparatus of this invention, the ignition provided by the flame front is progressive to provide an enhanced discharge pressure. Also, the combustion apparatus of this invention is illustrated as providing for the coating of a workpiece with a particulate material.

[ Oct. 7, 1975 VALVELESS COMBUSTION APPARATUS Rosser B. Melton, Jr., Helotes, Tex.

[73] Assignee: Southwest Research Institute, San

Antonio, Tex.

22 Filed: Feb. 21, 1974 21 Appl. No.: 444,403

[75] Inventor:

[52] US. Cl. 239/13; 239/81; 431/158 [51] Int. Cl. B0513 1/24; BOSB 17/04; F23R 1/00 [58] Field of Search 239/79-81,

[56] References Cited UNITED STATES PATENTS 1,702,731 2/1929 Hymer 431/158 X 2,714,563 8/1955 Poorman et a1. 239/85 X 3,015,127 1/1962 Stalego 431/158 X 3,156,454 11/1964 Flynn 431/158 X 3,194,295 7/1965 Marchal et al 431/158 X 3,320,999 5/1967 Stalego 431/158 3,357,375 12/1967 Brophy 431/8 X 3,376,098 4/1968 Pryor 431/158 X 3,693,875 9/1972 Shepard... 239/13 X 3,716,000 2/1973 Holden 431/2 X 3,801,346 4/1974 Melton et a1. 239/81 X Primary Examiner-Robert S. Ward, Jr.

[5 7] ABSTRACT Valveless combustion apparatus are disclosed in which a flame front from gas ignited in one part of the apparatus is utilized to ignite a charge of gas in another part of the apparatus that is open to atmosphere or other relatively low pressure. The ignition occurs before the charge of gas is dissipated from the part of the apparatus open to the lower pressure so that a high energy blast of gas can be directed from the apparatus to perform work. In one form of the combustion apparatus of this invention, the ignition provided by the flame front is progressive to provide an enhanced discharge pressure. Also, the combustion apparatus of this invention is illustrated as providing for the coating of a workpiece with a particulate material.

25 Claims, 9 Drawing Figures U.S. Patent Oct. 7,1975 Sheet 1 of2 3,910,494

-- I20psi I20 psi I20 psi FIG. 2B

US. Patent 0a. 7,1975 Sheet 2 of2 3,910,494

60 psiik u-l I20 psi I20 psi I20 psi 60 psi VALVELESS COMBUSTION APPARATUS This invention relates to valveless combustion apparatus for providing and directing a high pressure blast of gas to accomplish work. In one of its aspects, it relates to such an apparatus which may be used to coat a workpiece with a particulate material.

The term valveless is used herein to refer to the use of an apparatus including a chamber in which the relatively high pressure blast is generated that is open at one end to atmosphere or some other relatively low pressure, and does not require an outlet valve to hold pressure therein prior to discharge.

There are a number of situations in which a fuel-air explosion may be utilized to provide a directed blast of gas to accomplish a particular task. Samples of such situations are shown in U.S. Pat. Nos. 3,461,577, 3,572,273, and 3,713,496, all related to earth moving or fracturing, and the principles of the present invention are applicable to such. Another important example of the use of such a directed blast of gas is the application of a particulate coating material to a workpiece, such as the coating of stainless steel with tungsten carbide. In the prior art, numerous apparatus and systems have been provided for this type of application. For example, in one such prior system, a combustible gaseous mixture is ignited in a combustion chamber at the upstream end of a barrel which is sufficiently long to permit a supersonic detonation wave to be established and travel down the barrel. By the use of special detonable fuels which react rapidly and easily once the process starts, unignited gas is ignited by compression, sustaining the detonation wave. Downstream of the combustion chamber, particulate coating materials are fed into the gun barrel so that the particles are carried down the barrel at high velocity and directed against a suitable workpiece. However, the size of this particular apparatus has proven to limit its use and also its use involves a certain amount of danger because the use of highly volatile materials to obtain the detonation waves at sufficient energy.

In order to obviate some of the difficulties of this type of apparatus, apparatus was developed as described in US. Pat. No. 3,801,346, entitled METHOD AND AP- PARATUS FOR APPLYING PARTICULATE'COAT- ING MATERIAL TO A PIECE OF WORK. The apparatus disclosed therein directs a particulate coating material against a workpiece in a series of pulses, and does not require the generation of a detonation wave. Each pulse includes an initial step of feeding a charge of gas eous combustible mixture into a combustion chamber provided with an outlet nozzle. The combustible mixture is ignited and the outflow of gaseous mixture through the nozzle is constricted sufficiently to cause a rapid pressure rise during combustion of the mixture to peak value followed by a period of falling pressure during the continued outflow of the combusted mixture through the nozzle. A charge of the particulate coating material is injected into the combustion chamber for a period commencing just prior to ignition and the outflow of combustion mixture and entrained particulate material is directed against the workpiece at high velocity to cause the particulate material to form a coating on the workpiece.

In the type of applications discussed, the gas discharge must be released in no more than about 10 milliseconds from the apparatus and sometimes in less time.

If an outlet valve is used for closing a chamber to permit pressure to build up therein, this means that the valve must open up in IQ milliseconds, or preferably in less time. The design and utilization of such a valve adds complications and cost to any of the apparatus described, and effects its reliability. An important feature of the apparatus of US. patent application Ser. No. 198,806 is that it does not employ an outlet valve, but

rather an open but restricted outlet. By causing com-- plete combustion to occur in a relatively short time, the combustion will be complete in substantially less time than is needed for the escape of gas from the combustion chamber through the restricted opening.

The present invention is directed to improved combustion apparatus which provides for even more rapid combustion to permit the generation of a high pressure blast of gas which simulates a detonation wave without the use of highly volatile fuels needed to obtain a detonation wave, or the use of an outlet valve from a charging chamber.

In all the embodiments of this invention, an initially ignited fuel-air mixture is utilized to ignite unburned fuel-air mixture as it moves out of the apparatus so that ignition will be complete in substantially less time than is needed for escape of the fuel-air mixture from the apparatus. This is accomplished by providing a combustion apparatus including an ignition chamber connected to a source of a fuel-air mixture, and a main discharge chamber, which may include a barrel extension, and which is open at one end to the atmosphere, or some pressure lower than the charge pressure in the chamber. The chambers are initially charged with a fuel-air mixture and means is provided between the chambers for conducting ignited fuel-air mixture in the ignition chamber into the main chamber to aid in the combustion of the fuel-air mixture in the main chamber. As a preferred form of the present invention, this means is an elongated tube including spaced perforations therein so that as a compression wave passes by each of the perforations, it is progressively ignited by a flame front directed into the elongated tube. Means may be connected into the apparatus for injecting a quantity of a particulate coating material therein which is then discharged from the apparatus by the blast of high pressure gas and directed to coat a workpiece.

Referring now to the drawings, wherein like reference numerals are used throughout to designate like parts, and wherein preferred embodiments of the present invention are illustrated,

FIG. 1 is a perspective view with a partial cutaway of one form of the combustion apparatus of the present invention;

FIG. 2A is a perspective view with partial cutaway of another form of the present invention;

FIG. 2B is a graph showing the pressure at various points in the apparatus of FIG. 2A;

FIG. 3 is a sectional view taken at 33 in FIG. 2A;

FIG. 4 is an enlarged view taken at 4 in FIG. 2A;

FIG. 5A is a diagrammatic view and FIG. 5B is a graph illustrating the decreased discharge pressure provided when the apparatus of FIG. 2A is not utilized.

FIG. 6 is a diagrammatic view of another form of the present invention which is illustrated as being adapted for a particulate coating application; and

FIG. 7 is a sectional view taken at 7-7 in FIG. 6.

Referring now to FIG. 1, a relatively simple apparatus is shown therein which provides very rapid combustion of a fuel-air mixture, withoutthe use of detonable fuels. As illustrated in FIG. 1, a combustion apparatus is provided which includes a housing 11 having an enlarged, generally spherical, intermediate section 12 having a hollow interior, a discharge section 13 in the form of a hollow cylinder connected for communica tion at one end into section 12, and open to atmospheric pressure at its other end to form a discharge outlet for apparatus 10, and a cylindrical section 14 mountedon the opposite side of section 12 from section 13. Cylindrical section 14 is also hollow and is closed at its end opposite to the end connected to section 12 by a wall 15. Mountedinside of section 14, on the inside of end wall 15, is a smaller cylindrical member 16 which includes an opening 17 at its end opposite to end wall 15. Member, 16 is also hollow and a fuel-air mixture inlet 18 is connected throughwall into the interior of member 16 to permit the interior of member 16 and the interior of section 14, through opening 17, to be charged with a fuel-air mixture, such as gasoline or propane and air. A spark plug 19 orother ignition means is illustrated as mounted on wall 15 and extending into the interior of member 16 in order to ignite the fuel-air mixture therein.

Also mounted on the interior of section 14 and extending through the wall of section 12 and into the interior thereof is a tube 20 having spaced perforations 21 therein. Tube 20 is hollow and open at both endsso that the charging fuel-air mixture inside of section 14' is also caused to move through tube 20 into the interior of section 12. Perforated tube 20 extends through a substantial length of section 12 and ends adjacent to I discharge outlet 13 as shown in FIG. 1. I

Also mounted in section 14, between cylindrical member 16 and perforated tube 20 is a baffle plate 22 which functions to disperse flame emerging from opening 17 throughout the interior of cylindrical section 14.

As. is apparent from the above description, combustion apparatus 10 includes three separate chambers, i.e., a preignition chamber V formed by cylindrical member 16, an igniting chamber V formed by cylindrical section 14, and a main chamber V formed by enlarged spherical section 12. 'With this arrangement, fuel-air mixture enters inlet 18 displacing burned gas from a previous operation and charges the threechambers described. If desired, separate charging inlets could be provided for each of the chambers, although the arrangement described has proven to be satisfactory. Upon filling the respective chambers, and before the fuel-air mixture'in chamber V has a chance to escape out discharge outlet 13, spark plug 19 is activated to ignite the mixture in chamber'V which then'expels flame out opening 17 and into chamber V Baffle plate 22 serves to cause the flame to spread out over a wide area in chamber V in order to increase the pr gess of inflammation. The chamber V then rapidly becomes perforations 21 and causes near simultaneous, rapid combustionin every portion of chamber V and the ignited gas in chamber V is then discharged asa blast I from discharge outlet 13.

With the arrangement described, the combustion is so rapid in chamberV that the requirement for an out.- let valve in order to permit the pressure to build up is obviated. This is accomplished by utilizing a part of the fuel air mixture initially ignited to ignite the rest of the fuel-air mixture to provide a vigorous, widely distributed ignition in the main chamber. The apparatus of FIG. I has proved satisfactory for maintaining volumes from 1.2 cubic feet up to cubic feet and it is believed.

that this can be extended to larger or smaller sizes. As is obvious. it contains'no moving parts andachieves burning of gas in the main chamber at times of 2 to 5 milliseconds depending on its size.

In order to improve the rate of combustion and increase the discharge pressure, it is possible to, coordina te ignition and combustion in an elongated tube so that the first part of the gas to burn (at the rear of the.

tube) would compress the unburned gas ahead of it.

This compressed gaswould then itself be ignited and,

, of the resulting blast.

filled with the flaming gas and as the chamber becomes filled, flaming gas reaches the input of perforated tube 20. The entrance to tube 20 is located in the central portion of chamber V and behind baffle plate 22 so that the flame reaches it last, after inflammation is nearly total. Consequently, once the flame begins to flow down perforated tube 20, it does so with nearly the FIGS. 2-7 show embodiments of this invention which are similar to that in FIG. 1, but in which progressive combustion such as described is employed in order to enhance the force of the resulting blast and increase the efficiency of the device. FIG. 2A illustrates one.

form of apparatus employing the progressive combustion concept which has proved to be satisfactory, and FIG. 6 illustrates a modified version of this device. Both the embodiments of FIG. 2A and FIG. 6 are shown .for

V a specific application of a coating of a particulate material on a workpiece, however, it is to be understood that these devices may be used for many other applications where it isdesired to direct a high energy blast of gas for work.

As shown in FIG. 2A, a combustion apparatus 30 includes an elongated cylindrical housing 31 having a main chamber portion 32 of relatively large diameter and a barrel portion 33 of relatively smaller diameter extending from portion 32. As illustrated, the end of portion 32 away from barrel portion 33 includes a partition 34 dividing portion 32 into an ignition chamber 35 anda main chamber36. Main chamber 36 is in communication with the interior of barrel portion 33 and the end of barrel portion 33 opposite from portion 32,

is open to the atmosphere.

A fuel-air mixture inlet 37 is connected through an end wall 38 of mainportion 32 to permit the mixture to charge chamber 35. Also, a spark plug or other igni tion means 39 is connected through the wall portion 32 into chamber 35 to provide for, ignition in this chamber.

An elongated igniter tube 40 extends from chamber 35, through partition 34 into chamber 36 and through a substantial portion of the length of barrel portion 33.

Beginning from a point just beyond where tube 40 emerges from chamber 36 into the interior of barrel 33, a plurality of spaced prongs 41 are provided as illustrated in FIG. 2A. Prongs 41 may be provided in spaced rows of four prongs which are equally spaced about the periphery of tube 40 and each adjacent row of four prongs may be offset by 45 from the adjacent row (only two such prongs in each row are illustrated in FIG. 2A for simplicity). As illustrated in FIG. 4, prongs 41 include member 42, which may be of angle iron, disposed at an angle, for example, 45, with respect to tube 40, and a strut member 43 connecting the outer end of angle member 42 to tube 40. Member 42 is located on tube 40 so as to be directly over one of a plurality of spaced perforations or openings 44 provided in tube 40 to permit flame from the interior of tube 40 to be conducted into the interior of the barrel 33. In

this manner each of prongs 41 is disposed over an opening 44 to act as a flame holder to control flame emerging from each of the openings 44.

Unlike the apparatus of FIG. 1, ignition of the gas charge in main chamber 36 is provided by a separate ignition means than that provided in chamber 35. For this purpose a small sleeve 45 open at one end and encircling tube 40 at the other end is provided in the sec tion of chamber 36 formed by portion 32 of housing 31. Sleeve 45 includes a first cylindrical portion 46 having spaced openings 47 and a second cylindrical portion 48 of a larger diameter than portion 46, and a spark plug 49 or other ignition means is mounted in portion 48 for igniting a charge of gas therein which is then expelled out the open end of sleeve 45 and out openings 47. A baffle plate 54 also may be provided adjacent the open end of sleeve 45 for dispersing the ignited gas into chamber 36. An inlet 50 may be provided in the wall of portion 32 of housing 31 for connection to a source of fuel-air mixture (not shown), such as propane or gasoline, for charging the interior of chamber 36 prior to ignition.

Thus, as the fuel-air mixture charge in chamber 35 is ignited, a flame front is caused to move down igniter tube 40 to provide progressive sources of ignition as flame emerges from openings 44. Also, as fuel-air mixture charge in chamber 36 is ignited, starting inside of sleeve 45, the charge in chamber 36 is compressed and moves as a compression wave along chamber 36 towards the outlet thereof. As the compressed gas flows by the various openings 44, combustion progressively occurs to simulate detonation that occurs with a detonation wave, causing a higher outlet pressure than if the progressive combustion were not employed. The graph of FIG. 28 illustrates the relative pressure at various stages of the apparatus. In contrast, FIGS. 5A and 58 represent the discharge pressure obtained with a similar apparatus except without the spaced openings44 so that the progressive combustion following compression does not occur. As noted by comparing FIGS. 2B and 58, with the use of progressive combustion provided by igniter tube 40, a peak pressure near the outlet of the apparatus of about twice of that without progressive combustion is provided.

By way of example, the apparatus of FIG. 2A can be used to coat a workpiece (not shown) with a particulate coating material. For this purpose, means such as an inlet conduit 51 (see FIG. 3) may be provided to permit the injection of a coating material 52 into and about the interior of barrel portion 33 of housing 31. It is preferred that inlet conduit 51 be offset from the center of barrel portion 33 so that the particulate material will be injected substantially on the path shown by arrow 53. Conduit 51 can be connected to suitable apparatus (not shown) for providing a source of particulate material suchas illustrated and described in copending patent application Ser. No. 198,806, referenced above.

Referring now to FIGS. 6 and 7, a form of this invention is illustrated that is particularly adapted to apply a coating to a workpiece at a relatively high impact velocity to thereby form relatively dense and adherent coatings. As illustrated, a combustion apparatus is provided which includes a cylindrical housing 61 having an elongated barrel portion 62 forming a main duct, and an ignition portion 63 of larger diameter than barrel portion 62. Portion 63 forms a drive chamber and is in open communication with barrel portion 62. The end 62a of barrel portion 62 away from ignition portion 63 is open to atmosphere and the opposite end 630 of housing 61 is closed.

Centrally mounted in housing 61 and extending from wall 63a to adjacent open end 62a is an igniter tube 64 which includes a plurality of retarder sleeves, shown as four sleeves 65, 66, 67 and 68, spaced along it. Each of the retarder sleeves includesa plurality of spaced perforations 69, and the end of igniter tube 64 adjacent open end 62a includes spaced perforations 70. The interiors of igniter tube 64 and retarder sleeves -68 are hollow and in communication with each other. As illustrated, an end 64a of igniter tube extends through wall 63a for receipt of a charge of a fuel-air mixture such as gasoline or propane.

A pair of conduits 71 and 72 are connected into barrel portion 62 as illustrated, generally near open end 62a, for the injection of a particulate coating material into housing 61. Again, conduits 71 and 72 may be con-v nected to suitable apparatus (not shown) for providing a source of particulate material such as illustrated and described in co-pending patent application Ser. No. 198,806, referenced above.

In operation, housing 61 is filled initially, including all of the internal piping, with a flammable mixture which can consist of air plus almost any fuel, by injecting the mixture into the open end 64a of igniter tube 64. A small quantity of powdered coating material having the right size and composition is then injected into the main duct formed by barrel portion 62, where it will remain suspended momentarily. Next, by appropriate means (not shown) high pressure burning gas (the result of burning some of the same fuel-air mixture, usually) is injected into the igniter tube 64. This gas rushes down the tube and initiates burning in the retarder sleeves 65-68 as it reaches each in turn and finally ignites the gas in the main duct atthe far end of the igniter tube. There is a delay between the time at which the igniting gas issues through perforations 64b in tube 64 and ignites the retarder sleeve contents and the time that flame spurts from the retarder sleeves through perforations 69 to ignite the gas around it; this delay is made to be greatest for the first retarder sleeve 65 and least for the retarder sleeve 68. This gives an apparent rate of progress of ignition of (and combustion in) the main duct which greatly exceeds the actual rate of progress of the igniting gas down igniter tube 64 and the result is that a strong blast wave is generated which would not otherwise result and the suspended, injected powder is first accelerated and subsequently heated,

being finally blown out the end of the main duct, impinging on and adhering to a surface (not shown) to form a coating.

The blast wave generated results from the unburned gas first being, compressed due to an explosion in the driving chamber formed by portion 63 of housing 61, and second being burned by ignition from theretarder sleeves. The net effect of compression followed by combustion is to produce a much stronger and fastermoving disturbance than would result from a gas explosion in just the driver chamber.

This blast wave has much in common with a so-called detonation wave (probably the most violent combustion mechanism observed in gaseous combustion) except that detonation occurs'only with certain special fuels and/or oxygen-enriched mixtures while this invention accomplishesthe same result with essentially any fuel. A detonation wave depends on self-ignition of a combustible mixture behind a combustionproduced pressure wave, and there are not very many mixtures which will self-ignite from their own combustion pressure and, therefore, detonate. if on the other hand, proa secondchamber in said housing in communication with and adjacent said first chamber at one end,

said second chamber being open at its other end to the atmosphere to form a discharge outlet for said housing; means for igniting said fuel-air mixturein said first chamber; and means extending from said first chamber into said second chamber to distribute ignitedfuel-air mixture from said first chamber into said second chamberv to cause combustion of a fuel-air mixture in said second chamber. 2. The combustion apparatus of claim 1 whereinxsaid last mentioned means is a tube having spaced perforations, therein extending from said first chamber into a substantial portion of said second chamber.

gressive ignition is supplied externally with the right timing and at the correct location, the disturbance created is not in any essential respect different from a detonation, except that a non-detonatable" mixture is in volved.

Use of progressive combustion will tend to produce maximum coating powder velocity and only a moderate amount of exposure to hot gas, due to the high velocity of expulsion and the short residence time in the barrel. The concept of progressive combustion is flexible with respect to the type of combustion produced if one ignites the driving duct in other ways and possibly omits the driving chamber. For instance, using the igniter tube (retarder sleeve concept) it is easily possible to ig nite the whole duct essentially simultaneously and obtain less particle velocity and more particle heating, al-

ducing a low velocity expulsion of gas that would be appropriate for powders requiring low impact velocity but extended heating time.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus. V

it will be understood that certain features andsubcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is-within the scope of the claims.

As many'possible embodiments'may be made of the invention without departing from the scope thereof, it is to be understood that allmatter herein set forth'or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A combustion apparatus for generating and direct ing a high pressure blast of gas comprising,in combination:

a housing;

a first chamber in said housing having a fuel-air mixture inlet;

3. The combustion apparatus of claim 2 further including a plurality of flame holders disposedon said tube, each of said flame holders being adjacent a perforation therein.

4.'The combustion apparatus of claim 3 wherein each of said flame holders is disposedat an acute angle with cluding baffle means located in said first chamber for dispensing ignited gases therein.

8. The combustion apparatus of claim 1 further includingmeans for igniting said fuel-air mixture in said second chamber to establish a moving front of ignited gas moving towards said discharge outlet, and wherein said last mentioned means provides for progressive ignition of said front as it moves toward said outlet.

9. The combustion apparatus of claim 2 wherein said tube includes a plurality of retarder sleeves spaced along it, each of said.retardersleevesincluding spaced perforations therein.

10. The combustion apparatus of claim 9 further including means for injecting a particulate coating material therein to be carried fromsaid apparatus by said high pressure blast.

I 1. A method of generating and directing a high pressure blast of gas, comprising the stepsof:

charging a first zone and a second zone open to a relatively low pressure region with a combustible fuelair mixture, said first zoneand second zone being formed within an integral housing; igniting the fuel-air mixture in said first zone; and

conducting said ignited mixture from said first zone into said second zone by means of a conducting means extending from said first zone to said second zone and'attached to disperse said ignited mixture in order to ignite the fuel-air mixture in said second zone before itis dispersed out of said second zone to cause said high pressure blast of gas.

12. The method of claim 11 further including the step 5 I of progressively igniting the fuel-air mixture in said second zone and directing the resulting high pressure blast of gas to coat a workpiece with said particulate material.

14. The method of claim 12 further including the step of injecting a particulate coating material into said second zone and directing the resulting high pressure blast of gas to coat a workpiece with said particulate material.

15. A combustion apparatus for generating and directing a high pressure blast of gas containing a quantity of a particulate coating material comprising, in combination:

a housing;

a first chamber in said housing having a fuel-air mix-.

ture inlet;

a second chamber in said housing in communication with and adjacent said first chamber at one. end, said second chamber being open at its other end to the atmosphere to form a discharge outlet for said housing;

means for injecting a particulate coating material into said second chamber;

means for igniting said fuel-air mixture in said first chamber; and

means extending from said first chamber into said second chamber to distribute ignited fuel-air mix ture from said first chamber into said second chamber to cause the combustion of a fuel-air mixture in said second chamber.

16. The combustion apparatus of claim 15 wherein said last mentioned means is a tube having spaced perforations therein extending from said first chamber into a substantial portion of said second chamber.

17. A combustion apparatus for generating and directing a high pressure blast of gas, comprising, in combination:

a first pressure zone in which a fuel-air mixture can be ignited;

a second pressure zone adapted to be charged by a fuel-air mixture and in communication with said second zone, said second zone being open to a relatively low pressure as compared to the pressure of the fuel-air mixture charging said second zone; and

means extending from said first pressure zone into said second pressure zone for conducting ignited fuel-air mixture from said first zone into said second zone for igniting the fuel-air mixture in said second zone.

18. The combustion apparatus of claim 17 wherein said last mentioned means provides for progressive combustion in said second zone.

19. A combustion apparatus for generating and directing a high pressure blast of gas comprising, in combination:

a housing;

a first chamber in said housing having a fuel-air mixture inlet;

a second chamber in said housing in communication with and adjacent said first chamber at one end, said second chamber being open at its other end to the atmosphere to form a discharge outlet for said housing;

means for igniting said fuel-air mixture in said first chamber; and

a tube having spaced perforations therein extending from said first chamber into said second chamber to distribute ignited fuel-air mixture from said first I chamber into said second chamber to cause combustion of a fuel-air mixture into said second chamber.

20. The combustion apparatus of claim 19 further including a plurality of flame holders disposed on said tube, each of said flame holders being adjacent a perforation therein.

21. The combustion apparatus of claim 20 wherein each of said flame holders is disposed at an acute angle with respect to said tube.

22. The combustion apparatus of claim 20 further including means for injecting a particulate coating material therein to be carried from said apparatus by said high pressure blast.

23. The combustion apparatus of claim 19 wherein said tube includes a plurality of retarder sleeves spaced along it, each of said retarder sleeves including spaced perforations therein.

24. The combustion apparatus of claim 23 further including means for injecting a particulate coating material therein to be carried from said apparatus by said high pressure blast.

25. A combustion apparatus for generating and directing a high pressure blast of gas containing a quantity of a particulate coating material comprising, in combination:

a housing;

a first chamber in said housing having a fuel-air mixture inlet;

a second chamber in said housing in communication with and adjacent said first chamber at one end, said second chamber being open at its other end to the atmosphere to form a discharge outlet for said housing;

means for injecting a particulate coating material into said second chamber;

means for igniting said fuel-air mixture in said first chamber; and

a tube having spaced perforations therein extending from said first chamber into a substantial portion of said second chamber to distribute ignited fuel-air mixture into said second chamber to cause combustion of a fuel-air mixture into said second chamber. 

1. A combustion apparatus for generating and directing a high pressure blast of gas comprising, in combination: a housing; a first chamber in said housing having a fuel-air mixture inlet; a second chamber in said housing in communication with and adjacent said first chamber at one end, said second chamber being open at its other end to the atmosphere to form a discharge outlet for said housing; means for igniting said fuel-air mixture in said first chamber; and means extending from said first chamber into said second chamber to distribute ignited fuel-air mixture from said first chamber into said second chamber to cause combustion of a fuel-air mixture in said second chamber.
 2. The combustion apparatus of claim 1 wherein said last mentioned means is a tube having spaced perforations therein extending from said first chamber into a substantial portion of said second chamber.
 3. The combustion apparatus of claim 2 further including a plurality of flame holders disposed on said tube, each of said flame holders being adjacent a perforation therein.
 4. The combustion apparatus of claim 3 wherein each of said flame holders is disposed at an acute angle with respect to said tube.
 5. The combustion apparatus of claim 1 further including means for injecting a particulate coating material therein to be carried from said apparatus by said high pressure blast.
 6. The combustion apparatus of claim 3 further including means for injecting a particulate coating material therein to be carried from said apparatus by said high pressure blast.
 7. The combustion apparatus of claim 1 further including baffle means located in said first chamber for dispensing ignited gases therein.
 8. The combustion apparatus of claim 1 further including means for igniting said fuel-air mixture in said second chamber to establish a moving front of ignited gas moving towards said discharge outlet, and wherein said last mentioned means provides for progressive ignition of said front as it moves toward said Outlet.
 9. The combustion apparatus of claim 2 wherein said tube includes a plurality of retarder sleeves spaced along it, each of said retarder sleeves including spaced perforations therein.
 10. The combustion apparatus of claim 9 further including means for injecting a particulate coating material therein to be carried from said apparatus by said high pressure blast.
 11. A method of generating and directing a high pressure blast of gas, comprising the steps of: charging a first zone and a second zone open to a relatively low pressure region with a combustible fuel-air mixture, said first zone and second zone being formed within an integral housing; igniting the fuel-air mixture in said first zone; and conducting said ignited mixture from said first zone into said second zone by means of a conducting means extending from said first zone to said second zone and attached to disperse said ignited mixture in order to ignite the fuel-air mixture in said second zone before it is dispersed out of said second zone to cause said high pressure blast of gas.
 12. The method of claim 11 further including the step of progressively igniting the fuel-air mixture in said second zone with ignited mixture from said first zone.
 13. The method of claim 11 further including the step of injecting a particulate coating material into said second zone and directing the resulting high pressure blast of gas to coat a workpiece with said particulate material.
 14. The method of claim 12 further including the step of injecting a particulate coating material into said second zone and directing the resulting high pressure blast of gas to coat a workpiece with said particulate material.
 15. A combustion apparatus for generating and directing a high pressure blast of gas containing a quantity of a particulate coating material comprising, in combination: a housing; a first chamber in said housing having a fuel-air mixture inlet; a second chamber in said housing in communication with and adjacent said first chamber at one end, said second chamber being open at its other end to the atmosphere to form a discharge outlet for said housing; means for injecting a particulate coating material into said second chamber; means for igniting said fuel-air mixture in said first chamber; and means extending from said first chamber into said second chamber to distribute ignited fuel-air mixture from said first chamber into said second chamber to cause the combustion of a fuel-air mixture in said second chamber.
 16. The combustion apparatus of claim 15 wherein said last mentioned means is a tube having spaced perforations therein extending from said first chamber into a substantial portion of said second chamber.
 17. A combustion apparatus for generating and directing a high pressure blast of gas, comprising, in combination: a first pressure zone in which a fuel-air mixture can be ignited; a second pressure zone adapted to be charged by a fuel-air mixture and in communication with said second zone, said second zone being open to a relatively low pressure as compared to the pressure of the fuel-air mixture charging said second zone; and means extending from said first pressure zone into said second pressure zone for conducting ignited fuel-air mixture from said first zone into said second zone for igniting the fuel-air mixture in said second zone.
 18. The combustion apparatus of claim 17 wherein said last mentioned means provides for progressive combustion in said second zone.
 19. A combustion apparatus for generating and directing a high pressure blast of gas comprising, in combination: a housing; a first chamber in said housing having a fuel-air mixture inlet; a second chamber in said housing in communication with and adjacent said first chamber at one end, said second chamber being open at its other end to the atmosphere to form a discharge outlet for said housing; means for igniting sAid fuel-air mixture in said first chamber; and a tube having spaced perforations therein extending from said first chamber into said second chamber to distribute ignited fuel-air mixture from said first chamber into said second chamber to cause combustion of a fuel-air mixture into said second chamber.
 20. The combustion apparatus of claim 19 further including a plurality of flame holders disposed on said tube, each of said flame holders being adjacent a perforation therein.
 21. The combustion apparatus of claim 20 wherein each of said flame holders is disposed at an acute angle with respect to said tube.
 22. The combustion apparatus of claim 20 further including means for injecting a particulate coating material therein to be carried from said apparatus by said high pressure blast.
 23. The combustion apparatus of claim 19 wherein said tube includes a plurality of retarder sleeves spaced along it, each of said retarder sleeves including spaced perforations therein.
 24. The combustion apparatus of claim 23 further including means for injecting a particulate coating material therein to be carried from said apparatus by said high pressure blast.
 25. A combustion apparatus for generating and directing a high pressure blast of gas containing a quantity of a particulate coating material comprising, in combination: a housing; a first chamber in said housing having a fuel-air mixture inlet; a second chamber in said housing in communication with and adjacent said first chamber at one end, said second chamber being open at its other end to the atmosphere to form a discharge outlet for said housing; means for injecting a particulate coating material into said second chamber; means for igniting said fuel-air mixture in said first chamber; and a tube having spaced perforations therein extending from said first chamber into a substantial portion of said second chamber to distribute ignited fuel-air mixture into said second chamber to cause combustion of a fuel-air mixture into said second chamber. 